Ten thousand years after leaving a dying Earth, a human seedship arrives at a distant planet. The planet is covered three miles deep by an interlocking network of massive trees called the silva. The seedship lands, blasting a hole in the silva, and the ship's AI begins gestating the first generation of colonists.
Seventeen years later, a dozen colonists emerge. One of them kills a Waya, a wolf-like native sentient creature, triggering a battle in which all the colonists are wiped out.
The AI hatches a second generation and trains them to be warriors instead of explorers. But the Waya now face possible extinction from a plague that is disrupting their complex reproductive cycle. An uneasy truce is negotiated between the Waya and the humans, thanks to an unusual alliance between an aging, glowjuice addicted Waya and two human teenagers, Ricky and Marta. The two teens embark on a terrifying ascent to the top of the silva, the only way they can save the Waya and ensure their own survival.
As they climb they encounter alien life forms, meet an unexpected resident of the high silva, and eventually confront the true nature of the silva. The climax of the story involves an unusual solution that emerges from the interplay of several different sentient species, both organic and artificial.
Ascent to the Sun is a fast-paced hero's (and heroine's) journey, a tale of survival, interspecies conflict, and the search for coexistence.